Soft interior trim panels are currently used for vehicle interiors. These panels generally have an outer cover of leather, a plastic material that is similar to leather or a fabric material. A foam material on the back side of the outer cover provides the cover with a softer feel. A substrate is employed on the back side of the foam to support the foam and the outer cover and for mounting the soft interior trim panel in a vehicle. The outer cover or skin, foam backing and substrate in combination define a composite that is known as a soft feel composite.
Electrical switches are currently used in applications such as arm rests, console controls and the other interior trim components that are made of a soft feel composite. In some cases such electrical switches extend through an aperture in a bezel that passes through an aperture in a trim panel. Such electrical switches may either be secured to the bezel or attached to the same structure that the trim panel is attached to. These electrical switches and bezels are hard and rigid. The gaps and cracks formed between the bezels, switches, and a trim panel may catch on clothing and cleaning materials. The switches have crevices that are difficult or impossible to clean out, allow the passage of air and moisture and may transfer heat into or out of a vehicle passenger compartment. Furthermore, noticeable fit and finish problems can arise in such arrangement since it is difficult to always accurately fit a bezel around a switch component or switch array. An example of such arrangements is shown in U.S. Pat. No. 4,975,547.
Membrane switches may also be used in this type of application as is described in U.S. Pat. No. 5,448,028 issued Sep. 5, 1995 to Filion et al. Filion discloses a membrane switch supported by a trim panel beneath a layer of flexible skin. Other examples of multiple sheet membrane switches for interior applications are shown in U.S. Pat. Nos. 4,612,425 and 4,742,192. Such membrane switches are difficult to mold in place without introducing preload effects that can cause inadvertent accessory actuations. Moreover, membrane switches are "on-off" type switches that do not allow an occupant to vary the amount of electrical power flowing to the device that the switch controls.
U.S. Pat. No. 5,398,962 has a force-sensitive resistance sensor 30 having a low profile that is connected to the underside of a flexible outer cover and supported against a relatively rigid inner cover that overlies an air bag assembly. The sensor 30 is associated with a circuit that will compensate for thermal differences and includes a circuit that will provide a time delay before a given change in resistance will sound the horn. However, such an arrangement does not define a soft feel composite that is suitable for arm rest configurations or for protection against side impacts.
What is needed is an automotive interior door electrical switch array that is protected against fluid and dust contamination and is less disruptive of interior design contours such as smooth continuous trim panel surfaces and that will have a soft touch feel and also be able to compensate for changes in ambient conditions that might otherwise operate the switches. To accomplish this objective a conventional force-sensitive resistor sensor of the type shown in U.S. Pat. Nos. 5,222,399 and 5,086,652 is embedded in a soft feel substrate located in a side impact region of a vehicle wherein the soft feel substrate protects the switch mechanism. Furthermore, the switch mechanism is associated with a circuit that will prevent thermal expansion from adversely affecting the function of the array.